Large, skulky, and seldom-seen warbler. Typically found very low in dense tangles and thickets, where it walks along branches or on the ground. Breeds in boggy forest with spruce or tamarack. In migration, found where weedy fields meet a forest edge, especially with dense thickets, goldenrod, and jewelweed. A late spring migrant. Lemon-yellow below and olive-brown above with gray hood and complete white eyering. Female slightly duller than male. Immature has brownish hood, not gray. Similar to Mourning Warbler and immature Common Yellowthroat; look for complete white eyering, large size, long undertail coverts, and habit of walking rather than hopping.